Reactions of excited and ground state H3+ ions with simple hydrides and hydrocarbons: collisional deactivation of vibrationally excited H3+ ions

Kim, J.K.; Theard, Lowell P.; Huntress, W. T.

doi:10.1016/0020-7381(74)85001-1

Cited by 61 publications

(15 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Destruction is typically via photodissociation: for the M dwarf and T Tauri disks, this is again dominated by Lyman-α photons ). In the M dwarf disk, there are additional destruction routes via ionmolecule reactions with H + and H + 3 (Kim et al 1974;Smith et al 1992) and X-ray-induced photodissociation contributes at the level of 12−15% (similar to that found for C 2 H 2 and HCN). Similarly, the gas-phase abundance of OH is mediated by production via the photodissociation of H 2 O and the reaction between H 2 and O (Baulch et al 1992), with destruction via photodissociation and reactions with H 2 and H (Tsang et al 1986;Oldenborg et al 1992).…”

Section: Oh and H 2 Omentioning

confidence: 82%

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

Walsh

Nomura

Dishoeck

2015

A&A

186

329

View full text Add to dashboard Cite

Context. Near-to mid-infrared observations of molecular emission from protoplanetary disks show that the inner regions are rich in small organic volatiles (e.g., C 2 H 2 and HCN). Trends in the data suggest that disks around cooler stars (T eff ≈ 3000 K) are potentially (i) more carbon-rich; and (ii) more molecule-rich than their hotter counterparts (T eff > ∼ 4000 K). Aims. We explore the chemical composition of the planet-forming region (<10 AU) of protoplanetary disks around stars over a range of spectral types (from M dwarf to Herbig Ae) and compare with the observed trends. Methods. Self-consistent models of the physical structure of a protoplanetary disk around stars of different spectral types are coupled with a comprehensive gas-grain chemical network to map the molecular abundances in the planet-forming zone. The effects of (i) N 2 self shielding; (ii) X-ray-induced chemistry; and (iii) initial abundances, are investigated. The chemical composition in the "observable" atmosphere is compared with that in the disk midplane where the bulk of the planet-building reservoir resides. Results. M dwarf disk atmospheres are relatively more molecule rich than those for T Tauri or Herbig Ae disks. The weak far-UV flux helps retain this complexity which is enhanced by X-ray-induced ion-molecule chemistry. N 2 self shielding has only a small effect in the disk molecular layer and does not explain the higher C 2 H 2 /HCN ratios observed towards cooler stars. The models underproduce the OH/H 2 O column density ratios constrained in Herbig Ae disks, despite reproducing (within an order of magnitude) the absolute value for OH: the inclusion of self shielding for H 2 O photodissociation only increases this discrepancy. One possible explanation is the adopted disk structure. Alternatively, the "hot" H 2 O (T > ∼ 300 K) chemistry may be more complex than assumed. The results for the atmosphere are independent of the assumed initial abundances; however, the composition of the disk midplane is sensitive to the initial main elemental reservoirs. The models show that the gas in the inner disk is generally more carbon rich than the midplane ices. This effect is most significant for disks around cooler stars. Furthermore, the atmospheric C/O ratio appears larger than it actually is when calculated using observable tracers only. This is because gas-phase O 2 is predicted to be a significant reservoir of atmospheric oxygen.Conclusions. The models suggest that the gas in the inner regions of disks around cooler stars is more carbon rich; however, calculations of the molecular emission are necessary to definitively confirm whether the chemical trends reproduce the observed trends.

show abstract

Section: Oh and H 2 Omentioning

confidence: 82%

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

Walsh

Nomura

Dishoeck

2015

A&A

186

329

View full text Add to dashboard Cite

show abstract

“…References. (1) Manion et al (2013); (2) Peng et al (1999); (3) Demore et al (1997); (4) Tsuchiya et al (1994); (5) Millar et al (1986); (6) Herbst et al (1989); (7) Millar & Herbst (1990); (8) Decker et al (2001); (9) Prasad & Huntress (1980); (10) Hellberg et al 2005;(11) Abouelaziz et al (1992); (12) Kaminska et al (2008); (13) Montaigne et al (2005); (14) Kim et al (1974); (15) Anicich et al (1975); (16) …”

Section: Appendix B: Excitation Of Sulphur-bearing Molecules In Diffumentioning

confidence: 99%

Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope

Neufeld

Godard

Gérin

et al. 2015

A&A

103

View full text Add to dashboard Cite

We have observed five sulphur-bearing molecules in foreground diffuse molecular clouds lying along the sight-lines to five bright continuum sources. We have used the GREAT instrument on SOFIA to observe the SH 1383 GHz 2 Π 3/2 J = 5/2 ← 3/2 lambda doublet toward the star-forming regions W31C, G29.96-0.02, G34.3+0.1, W49N and W51, detecting foreground absorption towards all five sources; and the EMIR receivers on the IRAM 30 m telescope at Pico Veleta to detect the H 2 S 1 10 −1 01 (169 GHz), CS J = 2−1 (98 GHz) and SO 3 2 −2 1 (99 GHz) transitions. Upper limits on the H 3 S + 1 0 −0 0 (293 GHz) transition were also obtained at the IRAM 30 m. In nine foreground absorption components detected towards these sources, the inferred column densities of the four detected molecules showed relatively constant ratios, with N(SH)/N(H 2 S) in the range 1.1−3.0, N(CS)/N(H 2 S) in the range 0.32−0.61, and N(SO)/N(H 2 S) in the range 0.08−0.30. The column densities of the sulphur-bearing molecules are very well correlated amongst themselves, moderately well correlated with CH (a surrogate tracer for H 2 ), and poorly correlated with atomic hydrogen. The observed SH/H 2 ratios -in the range 5 to 26 × 10 −9 -indicate that SH (and other sulphur-bearing molecules) account for 1% of the gas-phase sulphur nuclei. The observed abundances of sulphur-bearing molecules, however, greatly exceed those predicted by standard models of cold diffuse molecular clouds, providing further evidence for the enhancement of endothermic reaction rates by elevated temperatures or ion-neutral drift. We have considered the observed abundance ratios in the context of shock and turbulent dissipation region (TDR) models. Using the TDR model, we find that the turbulent energy available at large scale in the diffuse ISM is sufficient to explain the observed column densities of SH and CS. Standard shock and TDR models, however, fail to reproduce the column densities of H 2 S and SO by a factor of about 10; more elaborate shock models -in which account is taken of the velocity drift, relative to H 2 , of SH molecules produced by the dissociative recombination of H 3 S + -reduce this discrepancy to a factor ∼3.

show abstract

“…can occur owing to collisions with the surrounding gas, mainly H2 and H. Quenching by H2 can occur either by vibrational transfer without atom transfer or by chemical reaction such as proton transfer.There are no direct measurements of rate coefficients of the elementary processes occurring during quenching by H2, but J. K Kim et al [1974]. measured a "phenomenological" transfer process in which the H2 gains 1-3 quanta of vibrational energy.…”

mentioning

confidence: 99%

“…We then test the sensitivity of the model to these assumptions. In the former case, we adopt the phenomenological rate coefficient of J. K Kim et al [1974]…”

mentioning

confidence: 99%

Densities and vibrational distribution of H₃⁺ in the Jovian auroral ionosphere

Kim¹,

Fox

Porter

1992

J. Geophys. Res.

View full text Add to dashboard Cite

Reactions of excited and ground state H3+ ions with simple hydrides and hydrocarbons: collisional deactivation of vibrationally excited H3+ ions

Cited by 61 publications

References 18 publications

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope

Densities and vibrational distribution of H₃⁺ in the Jovian auroral ionosphere

Contact Info

Product

Resources

About

Reactions of excited and ground state H3+ ions with simple hydrides and hydrocarbons: collisional deactivation of vibrationally excited H3+ ions

Cited by 61 publications

References 18 publications

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime

Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope

Densities and vibrational distribution of H3+ in the Jovian auroral ionosphere

Contact Info

Product

Resources

About

Densities and vibrational distribution of H₃⁺ in the Jovian auroral ionosphere